The present invention relates to a method and an apparatus for forming a multi-lobed winding for the stator of an alternator, particularly for use in the automotive field and of the type comprising turns defining a star-shaped configuration having a plurality of radial lobes alternated with hollows.
A method and an apparatus for forming a multi-lobed winding for the stator of an alternator are disclosed, for example, in Italian patent 1,157,040, corresponding to Barrera, Apparatus For Forming Stator Coils Of Dynamo Electric Machines, U.S. Pat. No. 4,512,376, both of which are incorporated herein by reference.
Typically, in the case of a three-phase alternator for automotive use, each stator is provided with a winding including three multi-lobed coils angularly shifted relative to each other. The coils are formed at different stages by the forming machine, and each coil has two wire terminal ends. Each of the three multi-lobed coils constituting one of the three phases of the winding is split into two semi-coils or semi-phases which are angularly shifted relative to each other by one lobe, so that the lobes of one semi-phase are opposite to the hollows between the lobes of the other semi-phase.
According to the prior art, the two semi-phases of each coil are made by the forming machine at two subsequent stages by cutting the supplied wire between one forming stage and the other, so that each semi-phase of the three winding phases in the finished winding inserted into the stator has a pair of terminal ends. This results in a total of twelve terminal ends.
A stator winding of undulatory type with a single continuous wire, including two multi-lobed coils shifted relative to each other by one lobe, has already been proposed. (See, for example, Taji et al., Armature Of A.C. Generator For A Car And Method Of Manufacturing The Same, U.S. Pat. No. 4,857,787 and parallel European patent 209,091, both of which are incorporated herein by reference). This method initially involves forming a single multi-lobed coil which is then split into two coils, without cutting the wire portion connecting them, one of the coils being overlapped on the other in at overturied position. This additional operation involves wasted time and a resulting decrease in the productivity of the machine.
In view of the foregoing, it would be desirable to provide a method and apparatus in which the final required configuration of the winding is obtained without additional operations after winding the wire by an apparatus which requires very small changes with respect, for example, to the apparatus taught in Italian patent 1,157,040 and corresponding U.S. Pat. No. 4,512,376.
It would also be desirable to provide a method and an apparatus for forming a multi-lobed winding for the stator of an alternator which enable the two semi-phases of each winding phase to be made continuously, without cutting the wire at the end of the forming operation of the first semi-phase, so as to simplify the operations which are necessary for forming the winding, as well as to obtain a finished winding with a lower number of terminal ends.
It would also be desirable to provide a method and an apparatus by which multi-lobed windings constituted by a plurality of coaxial superimposed multi-lobed coils having their lobes angularly shifted relative to each other can be obtained continuously.